1. Preheat oven to 475°.
2. Snap off and discard tough ends of asparagus; cut asparagus into 1-inch pieces. Combine asparagus, zucchini, and onion in a 15 x 10-inch jelly-roll pan coated with cooking spray. Drizzle with oil; sprinkle with garlic and 1/8 teaspoon salt. Stir gently until vegetables are coated. Bake at 475° for 18 minutes or until vegetables are crisp-tender and begin to brown, stirring once.
3. Meanwhile, pour milk into a medium saucepan; place over medium heat. Gradually stir in cornmeal and 1/4 teaspoon salt. Cook over medium heat, stirring constantly, 5 minutes or until very thick.
4. Immediately spoon cornmeal mixture onto 3 individual serving plates. Combine vinegar and sugar; sprinkle over vegetables. Toss well; spoon vegetables evenly over cornmeal mixture. Sprinkle evenly with cheese; sprinkle with pepper, if desired.